Corrosion resisting steel



Patented Nov. 15, 1938 5 UNITED STATES PATENT I OFFICE cmttfifiifim. a...

Mint 0. Elder, Cleveland Heights, Ohio No Drawing. Application March 23, 1936,

Serial No. 10,549 1 Claim. (cl. -125) steels in substantial amounts, greatly increases a the resistance thereof to atmospheric corrosion, without adversely affecting the other physical characteristics of the metal.- It has been disclosed in the prior art that the beneficial effects of phosphorus may be obtained without sacrificing other desirable properties of a steel, if copper is also included in certain proportions to the phosphorus content.

In my prior application, above referred to, I I

disclosed that a cheap, durable steel can be provided, which will have excellent resistance to atmospheric corrosion, by including phosphorus and copper therein in substantial amounts. Such a steel has proven to have remarkable resistance to atmospheric corrosion, as well as good ductility and notch toughness, but has further proven to have poor hot-working qualities, which have.

interfered with its commercial possibilities. This poor workability, which results from an impair- 'ment of the malleability of the steel while hot, I have definitely traced to the copper content, which must be proportionally high to off-set the ill-eflects of the phosphorus.

The present invention has for an object the provision of a steel that will embody all of the advantages sought for in my earlier application, without incurring any of the disadvantages thereof, as are outlined above. It contemplates the provision of a low-cost steel, and an art of making the same, which will have excellent properties of resistance to corrosion, ductility, toughness and malleability, and other desirable characteristics. Other objects and advantages will become apparent hereinafter.

The theory upon which my prior application was predicated contemplates that the phosphorus content in copper-bearing steel, if of substantial proportions, would render such steel extraordinarily resistant to corrosion, and that the copper would neutralize the deleterious influence of the phosphorus upon the physical properties of the metal, and, further, would augment the resistance thereof to corrosion. However, to be effective in the former regard, it was necessary to include copper in amounts that exceeded the maximum point of efliciency from a corrosion existing standpoint, and in such amounts as to impair the malleability of the steel. In copper bearing steels, it has been found that 0-15 per cent -copper will give essentially the same corrosion resistance values as greater amounts 10 thereof. Hence, it was concluded that-the copper employed in excess of this figure (0.15%) to counteract the influence of the phosphorus has little utility as a corrosion resisting agent,

but does adversely aflect the malleability of the 1 steel; whereas, 0.15 per cent copper or less, though satisfactory from every other standpoint, is insuflicient to overcome the bad effects of the phosphorus when the latter is employed, in such an amount as to be most effective as a corrosionre- 2o sisting addition to steel.

In seeking for some suitable element to take the place of copper in high phosphorus steels, which would aflford the advantages without the disadvantages thereof, I discovered that nickel could be employed to counteract the influence of the phosphorus, without impairing the hot-workability of the high-phosphorus steel, but that the corrosion resistance of the metal was in nowise developed as when copper was employed. Thus it was that the subject matter of the present application came into being.

According to the present invention, I provide a low-cost steel having good physical properties;

notably those of ductility, toughness, malleability and high-resistance to corrosion, by including in ordinary commercial steels; e. g., low-carbon Bessemer and basic open-hearth steels. amounts of phosphorus, copper and nickel in such proportions that the phosphorus functions with maxi- 4o mum efliciency, for the quantity added, to render the steel resistant to corrosion; the copper functions with maximum eiflciency, for the quantity added, to augment the corrosion resistance of the steel, and to partially overcome the deleterious influence of the phosphorus, and the nickel functions to complement the latter function of the copper to completely overcome the bad influences of the phosphorus, and to make possible the reduction of the copper content to the desired maximum.

I have ascertained that phosphorus reaches its maximum efliciency in improving the corrosion resisting properties of copper-bearing steel at or about 0.20'to 0.30 per cent inclusion, while copper,

' vention. If the phosphorus content is increased,

and the copper remains unchanged, the nickel content must be scaled-up accordingly. The precise proportions in which these variations may be accomplished are not definitely known, and each is best determined empirically, although it is not desirable to have the copper content substantially depart from 0.15 per cent. For phosphorus contents up to 0.4 per cent, the combined amounts of the copper and nickel inclusions should not be less than 0.4 per cent, and preferably-\higher. By maintaining the phosphorus and copper inclusions within the limits at which they function with maximum eilieiency as corrosion resisting agents, the amount of nickel required in addition to the copper content, for the outlined, can be minimized so that the steel does not appreciably exceed ordinary copper-bearing steels in cost. Thus, the preferred amounts of phosphorus, copper and nickel may bestated as follows:

. Per cent Phosphorus (maximum) 0.300 Copper (approximately) 0.150 Nickel (minimum) 0.250

A more speciflc analysis of commercial steels made in accordance herewith is as follows:

1 Per cent Phosphorus 0.20-0.30 Copper 4 4 0.15 Nickel (minimum) 0.25 Carbon (maximum) 0.30 Manganese do 0.30 Sulphurdo 0.05 Silicon do 0.25

Balance substantially iron.

Though the above ranges are permissible in the practice of my invention, I prefer to keep the carbon content below 0.10 per cent; the mangane'se content below 0.30 per cent, and the sulphur and silicon contents as low as possible.

In order that a comparison may be drawn between the steels made in accordance with the present invention, and other steels of both high and low alloy analyses, the following information is recorded. The values tabulated below are based on averages compiled from the analyses of many heats and the tests made on each, respectively:

Mn 8 Si P Cu Ni Or .28) .032 .298 .150 .370 .930 .290 .030 .007 .001 .020 Trace Trace In each case the balance of the steel is substantially pure iron.

-In this table, .heat A is an embodiment of the nickel-oopper-phosphorus steels of-the present invention; heat B is afli'igh' icopper-phosphorus steel; heat C is a relatively high alloy steel, characterized as one of the more expensive corrosion resisting steels, while heat D is a typical analysis of the average low carbon (non-alloy) steels.

Corrosion tests on these steels showed the following results, derived from exposing specimens purposes already of 40 gauge (W I; M) wire to atmospheric conditions-for periods of time as noted, and at geo-v graphically the same location (industrial environment):

Heat v Failed (more than 71%) ability and toughness, as will be seen from the following:

. Rolled at 1900 F. into- Ingots of- Billets Rods A No detects No defects.- B Seamy surtaoe.-. Bad scratches and slivers.

When these were later drawn into wire, heat A showed no defection of any kind and drew well, whereas heat 3 drew poorly and had to be scrapped. The malleability of steels made in accordance with this invention is by these tests shown to be greatly superior to that of high copper-phosphorus steels, for either hot or cold deformation, and is known to be equal to or better than the malleability of other steels, such as those represented by heats C and D.

The tensile values, (to which the ductility may be said to vary in inverse proportion), of these same steels, are as follow:

Here the ductility of steels made as per the teachings of this invention is shown to be comparable to that of ordinary low carbon steels, while high copper-phosphorus steels are shown to have very poor properties of ductility. Similarly in the "button test, wherein a. wire is wrapped around a mandrel of its own diameter to ascertain its toughness, steels of the A group have proved highly satisfactory, while those of the B group fail to meet the test without material defection.

From the foregoing it can be seen that I have provided a steel having unusual resistance to corrosion, with accompanying correspondingly good physical properties of malleability, ductility and toughness. The nickel-copper-phosphorus steels hereof closely resemble the higher alloy steels of group C, but have the marked advantage of ansonse perceded only by the high copper-phosphorus steels within their price level, but are far superior to the latter in most other respects. They equal the ordinary low cost steels in all physical values,

- except they are notably more resistant to corromarily concerned with the proportioning or the phosphorus, copper and nickel contents, relative to each other, to providethe best physical characteristics and resistance to corrosion possible in view of the amounts added.

Thus, to briefly recapitulate my invention, and

to summarize that which I apprehend as new, I

seek hereby to provide a low cost, corrosion resistins steel, marked by its cheapness of production, and good physical properties of ductility, toughness and malleabllity, in which phosphorus is present in amounts necessary to obtain the optimum in corrosion resistance: in which copper is present in amounts as will function with maximum efliciency to augment the corrosion resisting properties'ot the steel, and incidentally functioning to partially overcome the deleterious eflects oi the phosphorus content, and in which nickel is included in such an amount as is necessary'to complement the function or the copper to completely or substantially overcome the iii-eflects of the phosphorus inclusion. The nickel and the copper will jointly and severally preserve the physical properties of the steel: viz, thetouzhness, ductility and malleability thereof, while. the copper and the phosphorus will jointly and severally contribute to the resistance to corrosion of the steel.

The invention contemplates ordinary commercial iron or steel; e. 3., low-carbon Bessemer, basic open-hearth, etc., as the principal ileld oi application, which may include the usual amounts oi! silicon, manganese, carbon, sulphur, and other elements formed in commercial, low-cost steels,

'residually, or otherwise, and is not limited to the preferred analysis givenabove. In the following claim, where I have referred to the "Eo0d physical properties of my steel, this may be accepted as a comparative evaluation based on the tests hereinbefore set forth, from which.good properties may be objectively determined. Similarly, where]; have recited "low alloy" or low cost" steels, I intend by these words to cover steels having not in excess of .02% of other elements, such as, chromium, molybdenum, vanadium, and/or any other element or elements commonly employed as alloying additions to steel, except as are otherwise herein specifically set tcrth.

I claim:

A corrosion resisting steel possessing good physical properties of ductility, 'malleability, and toughness, containing copper in amounts ranging from 0.10% 'to 0.20%, inclusive, nickel from 0.15% to 0.35% inclusive, phosphorus from 0.20% to 0.40% inclusive, carbon not over 0.30%, manganese not over 0.30%, sulphur not over 0.05%, silicon not over 0.25%, and the balance by difference being substantially pure iron.

' Y C. ELDER. 

